Semiconductor devices are used in a variety of electronic and other applications. Semiconductor devices comprise, among other things, integrated circuits or discrete devices that are formed on semiconductor wafers by depositing one or more types of thin films of material over the semiconductor wafers, and patterning the thin films of material to form the integrated circuits.
Silicon oxide is used as an insulating layer in many such applications. For example, silicon oxide is frequently used as pre-metal dielectric (PMD) layer below the metallization layer and above the active device regions.
Silicon oxide is typically deposited by thermal oxidation or by using a chemical vapor deposition (CVD) process or a plasma enhanced CVD process. After depositing silicon oxide, it is usually etched to form a patterned structure. The etching may be performed using wet etching, which is usually isotropic. Anisotropic features in the deposited oxide are generally fabricated using plasma etching such as reactive ion etching.